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Old December 3rd, 2017, 01:42 PM   #1
stephen.woodbury
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Heartbeat Triggering Off of Change in Inputs and Outpus

In my lab we are using Controllogix plcs and RS 5000 for programming the PLCS.
We have one PLC on a skid, and one PLC at our workbench and we were getting them to communicate using a heartbeat trigger that we would set up

----[]timer.dn---------()TON timer 200ms.

We have 16 students in the class, trying to talk to 24 plcs. This was lagging the network a little bit.
Now our teacher wants us to set up a heartbeat trigger that will not lag the system down by triggering when we have a change in the input card.
We are using Factor IO software, one skid with wired start, stop, lights and we will be programming an HMI.

I am thinking I would need to use a read/write function to complete this and use an output coil.
I am wondering if there are any books out there that address this issue so I can read and see what the logic looks like?
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Old December 4th, 2017, 07:01 AM   #2
gclshortt
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http://www.plctalk.net/qanda/showthread.php?t=75078

http://www.plctalk.net/qanda/showthread.php?t=73591

http://www.plctalk.net/qanda/showthread.php?t=3315

Here are a few threads on the same issue. They may help you out.
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Old December 4th, 2017, 08:51 PM   #3
stephen.woodbury
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Thank you. I am doing my best to not be given the answers, but to critically think about what is happening.
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Old December 4th, 2017, 09:04 PM   #4
daba
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Most ControlLogix Input cards can be configured to initiate a "Change-of-State" event to the controller. It can be applied to specific inputs on the module, or, by default, all inputs. Look at the module configuration tabs to see how to set this up.

You can use this COS event to fire an EVENT task, into which you program whatever code you need to run when inputs change state.

Using this is the most efficient, there is no need to monitor for a change of state, it's all built into the hardware, you just need supporting software to make use of it, and of course that software will only run when it needs to.
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